when to put young chickens with older chickens and let them free range

[incubatorchick]

My younger chickens are about 10 weeks old I would like to put them out with the bigger once but i am hesitant, and they are RIR and black sex link i dont know if that matters or not.

 

[five is my dog]

my five 6 week olds are in with my hens and rooster. i just put my chicks in a dog cage in the coop at night and then when i put my chickens out to free range i would let the babys in the pen. i did this for 2 nights. i fenced off a section of the pen and put the chicks in there. and my adults in the other part. the only problem was that at the end of the 3 ft chicken wire there was a 3in space between the wire and the top of the coop. i went to church at 6 pm and they flew over the wire and went to bed with the adults. i let them stay and then they where fine the next day. so i let them out to free range only the babys wouldnt come out of the pen for a few days to free range but on day 3 they came out and free ranged.